Fiber conduit installation



Oct. 6, 936. H. SWEET 2,05,304

FIBER- CONDUIT INSTALLATION Filed Nov. 5, 1935 thereto.

- Patented Oct. 6, 1936 UNI-TED STATES 2,056,304 FIBER coNDUi'r INSTALLATION Harry Sweet, Berlin, N. H., assignor to Brown Company, Berlin, N. H., a corporation of Mame Application November 5, 1935, sei-iai N0. 48,333

. 2 Claims.

The subject of this invention is fiber conduit installation such as sometimes serves the purpose of housing subterranean electric-wiring systems, for instance, telephone-wiring systems. 'I'he 5 fiber conduit contemplated herein is manufactured in short lengths or sections which are joined end-to-end by couplings as they are being installed in the ground.

An objective of the present invention is to en-A l0 able a tight and leakproof coupling of ber contion are fiber-walled and are impregnated withv waterproofing binder lending good machinability Each section may be made by a wellknown practice which involves convoluting a wet web of interfelted cellulose bers onto a mandrel into a tube of the desired Wall thickness, removing `the tube from the mandrel, drying it, and impregnating it with the appropriate binder, Apreferably molten pitch or similar bituminous binder. The coupling used in the install-ation of the present invention may be fashioned yfrom shortpieces or collars of similar tubular stock, but the tubular stock for forming the coupling is preferably of a wall thickness distinctly greater than that of the conduit sections to be united thereby.'

The installation of the present invention will now be described in detail with reference to the accompanying drawing wherein,-

Fig. 1 represents a section through the coupledl end portions of a pair of installed conduit sections.

z Fig. 2 shows in perspective a coupling collar, part of which hasbeenlbroken away to reveal the internal collar wall.

As shown in Fig. 1, the pair of conduit sections joined in accordance with the present invention are relatively thin-Walled. By virtue of the thinness of their walls and theii` waterproofed ber structure, they are somewhat fragile, but they are quite hard and lend themselves nicely to machining. The coupling collar il, with which the adjacent end portions i2 Aas is usually done in this art.

of the conduit sections are in tight frictional engagement, is composed' of material similar to the conduit sections; and it is formed from a tubular piece of distinctly greater original wall thickness than the conduit sections.

In fashioning the coupling collar, the internal wall of a piece or collar of waterproofed ber tubing of the appropriate length and wall thickness is machined or cut, as on a lathe, to provide thereon an annular rib i3 substantially midl@ waythereoi and wall portions i4 immediately beyond the rib each of progressively and slightly increasing internal diameter toward the end of the piece. The end portion l2 of each conduit section is also machined or cut so that its exw ternal diameter progressively and slightly decreases toward its end. The taper or progressively decreasing external diameter thus produced at each end portion l2 is made to correspond exactly to, or be of minutely less angular- 20 ity or taper than, the progressively increasing internal diameter of the coupling Wall portion it, wherefore, each end portion i2 of a conduit section may be driven into a coupling Wall portion ifi and, under the radial forces set up during 25 driving,.yield a dry, exceedingly tight fit that prevents leakage of water into the conduit. The annular rib i3 on the internal wall of the coupling acts to prevent either end portion l2 from vbeing overdriven and thus causing a loose or open 30 joint at the coupling ends into which moisture would be apt to leak and thence work its way into the interiorl ofthe conduit and impair the electric-wiring system therein. It is desirable that the surface of the rib i3 iri the coupling eX- 35 tend, as shown, slightly below or outwardly of the internal faces or walls of the conduit sections iii. IIfhis is desirablel in that it obviates the possibility of an electric cable catching on the rib in being dragged through the installed conduit, 40

Of course, the surface of the rib might for the same reason be substantially flush with the internal surfaces or walls of the conduit sections.

The installation of the present invention is particularly advantageous when the water- Harrington joint which involves tapering the end portions of conduit sections While developing a shoulder at the large end of the taper functioning as a back-stop against overdriving of the sections into the coupling used in such form of 55 joint. The fact is that when, with such low wall thickness, an ample shoulder is left at the large end of the taper, the wall at the small end of the taper is so thin or reduced in substance that it is apt to crack or break under the severe stresses of driving the conduit section into the coupling. The present invention obviates or minimizes such danger, since the-end portion i2 of a conduit section can be maintained at sucient Wall thickness to the very small end of its taper to remain intact during the driving operation.

I claim:-

1. A conduit installation comprising a pair of relatively thin-walled fiber conduit sections impregnated with waterproong binder lending good machinability thereto and a coupling collar of similar material but of distinctly greater original wall thickness with which adjacent end portions of said conduit sections are in tight frictional engagement, the internal wall of said collar being machined to provide an inwardly pro'- jecting annular rib thereon and wall portions immediately beyond said rib each of progressively and slightly increasing internal diameter toward the end of said collar and the external wall of each conduit section being machined at its end portion to provide a tapered end portion of progressively and slightly decreasing external diameter corresponding to the progressively increasing internal diameter oi a collar wall portion,

said adjacent end portions of said conduit sections being forcibly driven into said collar wall portions and said peripheral rib serving to prevent either end portion from being overdriven.

2. A conduit installation comprising a pair of relatively thin-walled iiber conduit sections irnpregnated with waterprooiing binder lending good machinability thereto and a coupling collar of similar material but of distinctly greater original wall thickness with which adjacent end portions of said conduit sections are in tight frictional engagement, the internal wall of said collar being machined to provide an inwardly projecting annular rib thereon and wall portions immediately beyond said rib each of progressively and slightly increasing internal diameter toward the end of said collar and the external wall of each conduit section being machined at its end portion to provide a tapered end portion of progressively and slightly decreasing external diameter corresponding to the progressively increasing internal diameter of a. collar wall portion, said adjacent end portions of said conduit sections being forcibly driven into said collar wall portions and said peripheral rib serving to prevent either end portion from being overdriven and the surface of said rib lying at most no farther inwardly than to be substantially iiush with the internal wall surfaces of said conduit sections.

HARRY SWEET. 

